Wait to start param thread for when the link is open.

It was started on setting up the crazyflie, and if the crazflie is never closed
the thread will keep running. It makes more sense to start it when opening and
stop it when closing

Author: ToveRumar

cflib/crazyflie/__init__.py

@@ -119,7 +119,7 @@ def __init__(self, link=None, ro_cache=None, rw_cache=None):
         self.extpos = Extpos(self)
         self.log = Log(self)
         self.console = Console(self)
-        self.param = Param(self)
+        self.param = None
         self.mem = Memory(self)
         self.platform = PlatformService(self)
         self.appchannel = Appchannel(self)
@@ -137,8 +137,6 @@ def __init__(self, link=None, ro_cache=None, rw_cache=None):
 
         self.connected_ts = None
 
-        self.param.all_updated.add_callback(self._all_parameters_updated)
-
         # Connect callbacks to logger
         self.disconnected.add_callback(
             lambda uri: logger.info('Callback->Disconnected from [%s]', uri))
@@ -244,6 +242,8 @@ def open_link(self, link_uri):
         self.connection_requested.call(link_uri)
         self.state = State.INITIALIZED
         self.link_uri = link_uri
+        self.param = Param(self)
+        self.param.all_updated.add_callback(self._all_parameters_updated)
         try:
             self.link = cflib.crtp.get_link_driver(
                 link_uri, self.link_statistics.radio_link_statistics_callback, self._link_error_cb)